Alarm system for compass repeaters



March 24, 1953 w. B. JUPP ALARM SYSTEM FOR coMPAss REPEATERS Filed Deo.15, 1950 MN NN AMY o. f E Mw/fm AWO NM n I A .nm @fu M Men Patented Mar.24, 1953 UNITED STATES PATENT OFFICE Claims.

This invention relates to repeater or data transmission systems, whereinit is essentialptliat the observer of the repeater indicator be able torely implicitly upon its accuracy. It is therefore essential for theobserver to know whenever the repeater is not functioning properly. Thisis especially important in repeater Compasses used on ships andairplanes. In bad weather the navigator relies implicitly on thereadings of his steering repeater compass, which is actuated from amaster gyrocornpass down below decks and serious results would follow ifthe repeater failed without the navigators knowledge. Vhere the ship (oraircraft) is equipped with an automatic pilot from which the shipscourse is governed by a repeater compass from a master controller, analarm system is doubly essential, since failureof the repeater circuitin this case without the knowledge of the human pilot, would be likelyto ground the ship or cause a crash.

I am aware that alarm devices have been on the market for some time,which sound an alarm upon failure of the electrical supply to thetransmitter and repeater. Such an alarm, however, does not sound in allcases where the electrical system is faulty. Thus, if there is an opencircuit in the common supply lead beyond th alarm relay, an alarm mayr'not sound, or in case of a short circuit in the repeater, or othertrouble causing a greater current flow than usual through the repeaterand transmitter. n

According to my invention, I have devised an additional alarm circuitwhich will sound an alarm in cases where the present alarm system failsto function, and thus improve the safety of instrument navigation.

The primary object of the present invention is to provide an electricalsystem of this character that includes an alarm device situated at thebridge of theship that is operable when the system is not functioningcorrectly due to any electrical failure such as short or open circuitsVtherein or when the voltage supplied by the primary supply falls belowa predetermined value or when the power supply fails.

One of the features of the invention resides in the provision of acircuit including an alarm device rendered eiective by the operation ofa relay controlled by a Ynormally balanced differential relay having aseries coil and a shunt coil in the v also includes a switch that `isoperable to render ,y

both the holdingand alarm circuitsmeffective.

Other objects, features and structural details of the invention will beapparent from the following description when read in relation to theaccompanying drawing which shows a schematic view and circuit diagram ofthe improved system.

With reference to the drawing, a data transmission system embodying thepresent inventive concepts is shown to include a primary circuitenergized from a suitable source of direct current electrical energycontaining a data transmitter indicated at l and a repeater motorindicated at 2. As shown, the positive terminal of the D. C. supply isconnected to the transmitter by way ci lead 3. Lead 4 connects therepeater motor' 2 to the negative terminal of the source energizing thesystem.

As shown, the D. C. ele'ctrica1 transmitter includes a commutator 5 anda cooperating roller carriage E. The commutator is suitably xed and thecarriage is rotatably mounted at the center of the commutator beingoperatively connected by way oi' suitable gearing l, 8, 9 and l0 to thephantom ring H of a gyrocompass i2. A contact arm i3 held in place by aspring (not shown) connects the carriage 6 to the supply lead 3. Therollers of the carriage 6 contact the commutator 5 and the position ofthe carriage as determined by the gyrocompass or 'other reference deviceprovides the data transmitted to the repeater motor 2.

The commutator shown comprises twelve segments and correspondinglyspaced segments `a. are interconnected by lead Segments b and segments care connected by leads l5 and I6 respectively. The repeater motor 2 isprovided with a pair of coils for each of the commutator segments a, band c. Coils c of the step-by-step D. C. motor 2 are connected tosegments c of the commutator by way of lead Il. Coils o' are connectedto the segments b of the commutator by way of lead i8. Viead l connectsthe coils a and the segments a of the commutator. Coils bf and c areconnected by an output lead 2t which is connected in turn to lead i ofthe system. The armature of the motor 2 is indicated at 2l. Armature 2iis rotatably mounted and is operatively connected to an azimuth positionindicator cr compass card 22 of the repeater compass 2 by way ofsuitable gearing 22, 23, 24 and 25.

in the position of the system shown in the drawing, the carriage i3 iscontacting opposite segments c of the commutator and only coils a of therepeater motor 2 are energized. The armature accordingly takes theposition shown in the drawing in alignment with the coils a. In

explanation of Ahow the-transmitter and 'repeater motor operates, itwill be assumed that carriage 6 moves in a clockwise direction as viewedin the drawing so that the right-hand roller contacts the adjacentsegment b while the left-hand roller still remains on segment a. In thiscondition coils a.' and |b of the motorl 2 are energized equally and thearmature 2l moves clockwise to assume a position midway between thecoils a and b. With further movement of the carriage 6 in the samedirection, the carriage will only contact segments b of the commutator.This steps the armature of the motor around to a position in alignmentwith coils b of the repeater motor. In this manner, the repeater compass22 is operated to repeat the information provided by the master compass,the card of which is indicated at 26. Card 26 of the gyrocompass I2 isxedly connected to the phantom ring il.

inasmuch as the repeater at the bridge is utilized in coursedetermination and steering of the craft, it is necessary that theinformation thereat correspond with the information provided by themaster compass at all times. In this connection, an alarm device 28 isprovided at the bridge to call attention Ito the fact that the repeateris not operating correctly. The alarm device is shown diagrainmaticallyand may take the form of a buzzer, bell or light. Heretofore, alarmdevices of this character have been utilized in repeater systems but thesame has only been rendered operable when the voltage of the energizingsource for the system fails or diminishes below a predetermined value.As long as the voltage supplied the system from the source is up tovalue, the alarm device would not be effective even though theinformation transmitted by the system to the repeater motor is in error.In the improved system, short or open conditions that cause incorrectdata transmittal are detected and the alarm. device rendered effectiveto indicate the same.

In accordance with the invention, the improved system includes a,normally balanced differential relay 29 with a coil 36 connected inseries in the primary energizing circuit including lead 3, transmitterl, leads I1, i9, i9, motor 2, a fuse 3l, and lead 4. Relay 29 alsoincludes a coil 32 arranged in shunt relation in the primary circuit bylead 33 to lead 3, resistor 3, variable resistor 35, and lead 39connected to lead 4. The armature 31 is normally biased to an openposition relative to contact 38 by spring 39 whose tension can beadjusted by a thumb screw 45. Contact 39 is connected to lead 4 by wayof lead 4i. In the relay 29, the ampere turns of the shunt coil 32 areadusted by means of the resistors 34 and 35 to an equivalent of theaverage of the ampere turns in the series coil 99 with the motor 2having either two or four coils energized. For example, assume the relayshunt coil 92 is wound with 280 turns and the relay series coil is woundwith 360 turns. Also, assume that in a two coil position of the motor 2,.2 ampere flows through the repeater circuit. In this position, only apair Vof coils such as coils a are energized. Further, assume that in afour coil position of motor 2, .4 ampere news through the repeatercircuit. This position corresponds to one where both pairs of coils c'and b are energized. Therefore in the differential relay series coil 35,the ampere turns, with a double coil position of the motor 2, are 12provided by multiplying .2 with 360. ln the four coil position of themotor 2, the ampere turns in series coil 30 are 144 provided bymultiplying .Il with 360. The average ampere turns of coil 39 are 108.The shunt coil532 is then adjusted for 108 ampere turns. Screw 49 isadjusted so that the spring 39 holds the armature so that it will notpull in under either of these conditions. The spring 39 consequentlytakes cares of approximately 36 ampere turns unbalance to prevent therelay from closing when the carriage 6 goes from an c position to an a,bl position for from an a, b position to a b position.

In the event an open circuit condition should develop between thetransmitter I and motor 2, say for example in lead I9, no current flowswhen the carriage is positioned at shown and the series coil 39 wouldtherefore be deenergized. As the shunt coil is energized at this time,the 108 ampere turns thereof overcomes the 36 ampere turns of the spring39 and the armature 31 of the relay engages the contact 38. The samecondition occurs with an open in the circuit at the fuse 3|.

In the event of a short circuit condition across the segments of thecommutator 5, for example, the carriage 9 is then positionable toenergize coils a', bi and c of` the motor 2. In this instance, .6 amperewould flow through the motor 2 and the energization of series coil 39would correspond to 216 ampere turns. This causes an unbalance of 198ampere turns at the differential relay which being greater than the 36ampere turns taken care of by spring 39 would cause the armature 31 toclose against contact 38.

The normally ineffective or open circuit including the alarm device 28contains lead 42, the armi 43 of a normally closed switch 44, lead 45,contacts 45, 41 for the armature 48 of a second relay 49, lead 5c, aseparate source of D. C. electrical energy such as battery 5I and lead52.

A holding circuit is provided for relay 49 including lead 53 to lead 3,coil 54 of the relay, leads 55, 56, arm 51 of switch 44, lead 58,contacts 59, 69 for armature 6l of relay 49, and lead 62 to lead 4. Thearmatures 48 and 9| of relay 49 are biased to an open position relativeto the respective contacts 46, 41 and 59, 66 by means of spring 63. Thenormally ineffective or open holding circuit by-passes the differentialrelay 29 of the improved system and is included in the primaryenergizing circuit. Operation of the relay 49 renders eifective orcloses the alarm circuit when the armature 48 connects the respectivecontacts 46, 41. The holding circuit for the relay 49 is closed orrendered effective by operation of the differential relay 29 when thearmature 31 thereof connects the Contact 38. A circuit for rendering theholding circuit effective by closing the same at the contacts 59, G byarmaure 6|, includes lead 4, lead 4|, contact 38, armature 31. lead 64,lead 55, coil 54for relay 49 and lead 53 to lead 3. Thus, any conditionsufficient to op` lerate relay 29 whether the same is fluctuating orconstant is effective to hold the relay 49 so that the alarm devicefunctions as intended. Switch 44 is operable to open or renderineffective the holding and alarm circuits of the system when desired.

The described alarm circuit is also operable apart from the relay 49 bya third relay 65 connected to close the circuit when the voltagesupplied by the primary D. C. energizing circuit falls below apredeterminedvalue. Coil 66 of relay 65 is connected across leads 3 and4. The alarm circuit in this instance includes lead 61 to lead 45,contact 68, armature 69 of relay `65 and lead 10 to battery 5i, lead 52,device 28, lead 42 and sw1tch arm 43. The armature 69 is normally heldin anopen position relative to the contact ES by the energization ofcoil G6 by the primary circuit. If, however, the voltage of the primarycircuit falls below a predetermined desired value, the spring llconnected to the armature B9 is eiecive to pull the armature $9 againstcontact 68 and close the alarm circuit. This circuit is also broken bymeans of switch 43 when desired.

Since many changes could be made in the above construction and manyapparently widely dilerent embodiments of this invention could 'be madewithout departing from the scope thereof, it is intended that all mattercontained in the above description or shown in the accompanying drawingsshall be interpreted as illustrative and not in a limiting sense.

What is claimed is:

1. A compass repeater system comprising a transmitter, a repeater, anormally balanced differential relay having a iirst winding and a secondWinding, an electrical current supply, said transmitter, repeater, rstwinding being connected in series across said supply, said secondwinding being connected in parallel with the series connection of saidtransmitter, repeater, and iirst winding, and an alarm means, saiddifferential relay being connected to control said alarm means, wherebythe occurrence of an open or short circuit condition in the seriesconnection of said transmitter, repeater, and rst winding imbalancessaid differential relay to operate said -alarm means.

2. The compass repeater system as dened in claim l, wherein the alarmmeans comprises a second relay having a winding adapted to be connectedacross said supply by said differential relay and having a pair ofnormally open contacts, an electrical alarm device, and a separatecurrent source for said alarm device, said alarm device, pair ofcont-acts, .and separate supply forming a normally open series circuit,whereby said differential relay, on the unbalance thereof, operates toenergize the second relay to close said series circuit and therebyoperate said alarm device.

3. Ina compass repeater system, a transmitter, a repeater, a irst sourceor" electrical current, a normally balanced differential relay includinga iirst winding, a second winding, and a pair of normally open contacts,said transmitter, repeater and iirst winding being connected in seriesacross said first eurent source, said second winding being connected inparallel with the series connection of said transmitter, repeater andrst winding, a second relay including a winding connected in series withsaid differential relay contacts across said supply and including a pairof normally open contacts, an alarm device having a second source ofelectrical current, said alarm device, second source of current and pairof second relay contacts forming a normally open series circuit, wherebyupon the unbalance of said differential relay, said differential relaycontacts close to energize said second relay thereby closing said seriescircuit to operate the alarm device therein.

4. The compass repeater system of claim 3, wherein the second relai7further includes a holding circuit adapted to connect the winding of thesecond relay across said first source of current upon the energizationof said winding through said differential relay contacts thereby tomaintain a continuous operation of said alarm device.

5. A compass repeater system comprising a D. C. electrical transmitterhaving a plurality of pairs of stationary commutator segments and acooperating rotatable contactor element adapted rotatably to be drivenby a compass, a step-bystep D. C. repeater mot-or having a plurality ofstationary pairs of coils corresponding to said pairs of commutatorsegments and a cooperating rotatable armature element adapted rotatablyto drive a compass repeater card, said corresponding pairs of segmentsland coils being electrically connected together, a D. C. source ofsupply, a normally balanced differential relay having first and secondwindings, said contactor being adapted to interconnect correspondingpairs of segments and coils in series circuit with the rst winding ofsaid differential relay across said supply, said second winding of thedifferential relay being connected in parallel with said series circuit,and an alarm means, said dierential relay being connected to controlsaid alarm means, whereby the occurrence of an open or short circuitcondition in said series circuit acts to unbalance said differentialrelay and effect operation of said alarm means.

WILLIAM B. J UPP.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,229,939 Goldstein June 12, 19172,022,758 Corderrnan Dec. 3, 1935 2,052,057 Reid Aug. 25, 1936 2,278,939Muehter Apr. 7, 1942 2,461,075 Naylor Feb. 8, 1949

